1. Field of the Invention
The present invention relates to an optical disc apparatus. More particularly, the present invention relates to an optical disc apparatus capable of writing and reproducing information to and from an optical disc, and a method of writing information to the optical disc.
2. Description of the Related Art
Optical disks may generally be used as recording media for storing digital information, e.g., data, audio and video. Optical disks may be classified into postscript type optical disks, e.g., compact disc-read only (CD-R), rewrite type optical disks, e.g., CD-RW (read and write), and bulk optical disks, e.g., digital versatile disc (DVD)-R, DVD±R, DVD±RW, and DVD±RAM (random access memory). Current trends include miniaturizing a spot diameter using a high numerical aperture (NA) object lens, using increasingly shorter wavelength light sources, e.g., a semiconductor laser, and using a thin printed circuit board (PCB), which may increase storage capacity of the optical disks and/or decrease optical disk drive size.
Information may be recorded on such an optical disk using a light source, e.g., a laser diode. However, an optimum write parameter may change due to a characteristic of the optical disk and compatibility with an optical disk apparatus. For common optical disks, an optimum write process may be performed by storing write parameters of the common optical disks in firmware of an optical disk apparatus and reading the stored write parameters when information is recorded. That is, when an optical disk is inserted into an optical disk apparatus, unique information, e.g., a disk identifier (ID), etc., of the optical disk may be read, and then a write operation for recording information may be performed by specifying a maker and a model of the optical disk based on the read unique information. Write parameters (hereinafter, referred to as write strategies) may include a pulse width, a change position (speed), a write power of a light source, and a target β.
However, various kinds of optical disks in addition to common optical disks are available on the market. Furthermore, in view of the development of new optical disks, it is impractical to set optimum write strategies for all optical disks available on the market. Thus, for unknown optical disks, i.e., those whose write strategies are not stored in firmware, a write operation may be performed using a standard write strategy or a write strategy of an optical disk having a similar characteristic, e.g., a write strategy of an optical disk of the same maker.
Recently, the amount of data handled by users has increased significantly. Write time is proportional to the amount of information recorded. Thus, in addition to obtaining a desired write quality, a reduced write time, e.g., by realizing a high-speed write operation, may be demanded.
Thus, optical disk makers develop optical disks suitable for high-speed recording, and optical disk apparatus makers develop optical disk apparatuses capable of high-speed recording. In detail, optical disk apparatuses may realize high-speed recording using, e.g., a constant angular velocity (CAV) method or a partial constant angular velocity (PCAV) method.
Moreover, even for common optical disks, previously stored write parameters may not be optimal, e.g., due to differences between optical disk apparatuses, individual differences between the optical disks and/or operational environments. Therefore, when a write command is received by an optical disk apparatus, e.g., from a personal computer (PC), the optical disk apparatus may perform an optimum power control (OPC) to determine the optimum write power of a light source performing a write operation.
According to the OPC, test recording may be performed in an OPC-exclusive test area using previously stored write strategies, and whether a selected write strategy is appropriate from recorded data may be determined. If the selected write strategy is appropriate, user data may be recorded in a user data area based on the selected write strategy. If the selected write strategy is not appropriate, the write power of a light source may be determined based on a compensated write strategy, and then the data may be recorded in the user data area.
Based on the result of the OPC operation, a write operation of correcting a write strategy and writing information using the proper write strategy may be performed. Here, when a linear velocity at which a write operation is performed is gradually increased, as in a CAV or PCAV write technique, a write strategy originally stored cannot be applied without being altered. As such, the write operation may be performed by updating a write strategy stepwise according to a change in speed, as illustrated in FIG. 9.
In the conventional optical disc apparatus, it may be necessary to adjust an optimum write strategy even for a well-known optical disc. Here, write strategy adjustment may include adjustment of a pulse width, a change position (speed), a write power of a light source and/or a target β. The write strategy adjustment must be performed manually, e.g., whenever a new type of an optical disc is produced, and another write strategy adjustment may be needed whenever there is a change of a write speed, so frequent adjustments may be required to realize an appropriate write strategy.
In addition, as the capacity of well-known optical discs continues to increase, storage capacity for storing write strategy information also increases. In addition, since a write strategy may be changed by an entity error of the optical disc, an instrument error of the optical disc apparatus or an operating environment (temperature, etc.), a write strategy stored in firmware may not necessarily be appropriate. In particular, when a write strategy is greatly corrected during the OPC operation, a subsequent write strategy may not be appropriate, which may cause a write quality to deteriorate.